RESUMO
DNA replicative and repair machinery was investigated by means of different techniques, including in vitro nuclear enzymatic assays, immunoelectron microscopy and confocal microscopy, in apoptotic cell lines such as HL-60 treated with methotrexate, P815 and K562 exposed to low temperatures and Friend cells exposed to ionizing radiation. The results showed a shift of DNA polymerase alpha and beta activities. DNA polymerase alpha, which in controls was found to be the principal replicative enzyme driving DNA synthesis, underwent, upon apoptosis, a large decrease of its activity being replaced by DNA polymerase beta which is believed to be associated with DNA repair. Such a modulation was concomitant with a topographical redistribution of both DNA polymerase alpha and the incorporation of BrdUrd throughout the nucleus. Taken together, these results indicate the occurrence of a dramatic response of the DNA machinery, through a possible common or at least similar behaviour when different cell lines are triggered to apoptosis. Although this possibility requires further investigation, these findings suggest an extreme attempt of the cell undergoing apoptosis to preserve its nuclear environment by switching on a repair/defence mechanism during fragmentation and chromatin margination.
Assuntos
Apoptose , DNA Polimerase Dirigida por DNA/metabolismo , Animais , Apoptose/efeitos dos fármacos , Apoptose/efeitos da radiação , DNA Polimerase I/efeitos dos fármacos , DNA Polimerase I/metabolismo , DNA Polimerase I/efeitos da radiação , DNA Polimerase beta/efeitos dos fármacos , DNA Polimerase beta/metabolismo , DNA Polimerase beta/efeitos da radiação , DNA Polimerase Dirigida por DNA/efeitos dos fármacos , DNA Polimerase Dirigida por DNA/efeitos da radiação , Vírus da Leucemia Murina de Friend , Células HL-60/enzimologia , Células HL-60/ultraestrutura , Humanos , Hipotermia/enzimologia , Hipotermia/patologia , Leucemia Eritroblástica Aguda/enzimologia , Leucemia Eritroblástica Aguda/patologia , Sarcoma de Mastócitos/ultraestrutura , Metotrexato/farmacologia , Camundongos , Células Tumorais CultivadasRESUMO
To examine the effects of age and training on the active T subpopulation we considered elderly amateur cyclists over 65 in comparison with young amateur cyclists and young and aged sedentary healthy controls. Significant differences were observed between trained and sedentary elderly subjects consisting of an increase in the percentage of active E rosettes after 4 and 24 h of in vitro PHA stimulation, and of a decrease in the in vitro phosphorylation of phosphatydylinositol 4,5-bisphosphate (PtdInsP2) and a corresponding increase in phosphatydylinositol 4-phosphate (PtdInsP) in the early steps of the mitotic response. Our findings support the hypothesis of the involvement of inositol lipids in controlling the expression of lymphocyte surface receptors.